Mixers are used in engine aftertreatment systems for mixing of two or more fluids. The fluids may include an exhaust gas of an engine and a reductant for treating or reducing one or more constituents of the exhaust gas. A mixer may provide a swirl effect, turbulence or any other mixing effect to provide a uniform mixing of fluids. During the mixing, the fluid such as the reductant may contact and form deposits on the surface of the mixer. After prolonged use, the reductant deposits may block channels and/or passages provided in the mixer. This blockage of the passages may affect the efficiency of the mixer.
U.S. Published Application Number 2011/0308234 discloses a dosing and mixing arrangement. The arrangement includes a mixing tube having a constant diameter along its length. At least a first portion of the mixing tube includes a plurality of apertures. The arrangement also includes a swirl structure for causing exhaust flow to swirl outside of the first portion of the mixing tube in one direction along a flow path that extends at least 270 degrees around a central axis of the mixing tube. The arrangement is configured such that the exhaust enters an interior of the mixing tube through the apertures as the exhaust swirls along the flow path. The exhaust entering the interior of the mixing tube through the apertures has a tangential component that causes the exhaust to swirl around the central axis within the interior of the mixing tube. The arrangement also includes a doser for dispensing a reactant into the interior of the mixing tube.